The invention relates to the fabrication of integrated circuits. More particularly, the invention provides a method and apparatus for directing process gas through a processing chamber.
High density integrated circuits, such as very large scale integration (VLSI) devices, are typically formed on semiconductor wafers by subjecting the wafers to a number of deposition, masking, doping and etching processes. The wafers are placed onto a pedestal or susceptor within a process chamber and process gas(es) are delivered into the chamber onto the wafer to perform the various deposition and etching steps. For example, one typical process involves delivering SiH4 and N2 into the process chamber while applying resistive or conductive heat to form silicon nitride on the wafer. Once the appropriate layer of silicon nitride is deposited onto the wafer, the remaining plasma and gas residue are withdrawn from the process chamber.
One consideration in semiconductor processing is the application of process gases in a uniform and controlled manner across the wafer""s entire surface. This consideration is important in the fabrication of large scale integration (LSI) and VLSI devices since a large number of processing steps are generally used in sequence. To achieve uniform processing, existing systems typically introduce gases into the process chamber through a perforated face plate having a plurality of small openings for distributing the gas over the wafer. After the etching or deposition step has been completed, gas residue is withdrawn from the process chamber by a suitable vacuum source, such as a pump. To facilitate uniform pumping dynamics, the process gases will typically be discharged through a number of circumferentially spaced gas inlets in a pumping plate surrounding the susceptor. The gases are then delivered through outlets in the pumping plate into a pumping channel disposed radially outward from and underneath the susceptor.
Many existing systems for directing process gas through semiconductor process chambers suffer from a number of drawbacks. For example, one known device comprises a pumping plate that has a flange that surrounds a pumping plate with six holes. The pressure drop on the various sides of the pumping plate may be the same but the pressure drop from the top and the bottom of the pumping plate are different because the gas holes are restricted by the flange. This flow path tends to have varying pressure drops between the pumping plate and the chamber, thereby disrupting the uniform discharge of the gases about the wafer.
It is desirable to have methods and apparatuses for directing gas(es) through a process chamber that provide improved deposition uniformity.
Methods and apparatuses are provided for directing constituents through a processing apparatus, such as a vapor deposition chamber. In one aspect, a claimed apparatus comprises a pumping plate for a processing chamber having an annular body member wherein said body member has a first portion and a second defining a circumferential edge and a central opening. The first portion comprises a sidewall of the circumferential edge having a plurality of circumferentially spaced through holes and the second portion has comprises a lateral portion that protrudes from the circumferential edge, such that, in a processing chamber, the first portion defines a first gas flow region comprising the central opening and a second gas flow region comprising the lateral portion of the second portion. By defining two flow regions, the claimed pumping plate establishes a more uniform flow of gas inside a processing chamber over prior art structures which contributes to improved uniformity of film deposition on a substrate.
In another aspect, a vapor deposition processing apparatus includes an enclosure housing a process chamber and a susceptor disposed within the processing chamber for supporting a semiconductor wafer. The apparatus further includes a chamber lid and a perforated face plate for uniformly distributing process gases into the chamber onto the wafer. In this embodiment, the pumping plate has an annular body with an opening therethrough with a longitudinal component and a lateral component extending away from the opening and having a plurality of through holes circumferentially spaced about an axis along longitudinal component. The pumping plate is displaced in the chamber such that an area through the opening in the pumping plate defines a first flow region over a surface of the susceptor and the longitudinal component and the wall of the chamber define a channel of a second flow region. The defined flow regions contribute to more uniform deposition of films than prior art configurations.
Other aspects, features and advantages of the invention will be apparent from the accompanying drawings and from the detailed description that follows below.